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1.
Chemistry ; 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31826307

RESUMO

X-ray structures of the halo-substituted complexes [Fe III (5-X-salMeen) 2 ]ClO 4 (X = F, Cl, Br, I) at RT have revealed the presence of two discrete HS complex cations in the crystallographic asymmetric unit with two perchlorate counter ions linking them by N-H amine ···O perchlorate interactions. At 90 K, the two complex cations are distinctly HS and LS, a rare crystallographic observation of this coexistence in the Fe III -salRen spin-crossover (SCO) system. At both temperatures, crystal packing shows dimerization through C-H imine ···O phenolate interactions, a key feature for SCO cooperativity. Moreover, there are noncovalent contacts between the complex cations through type-II halogen-halogen bonds, which are novel in this system. The magnetic profiles and Mössbauer spectra concur with the structural analyses and reveal 50% SCO of the type [HS-HS] ↔ [HS-LS] with a broad plateau. In contrast, [Fe III (5-Cl-salMeen) 2 ]BPh 4 ·2MeOH is LS and exhibits a temperature-dependent crystallographic phase transition, exemplifying the influence of lattice solvents and counter ions on SCO.

2.
Dalton Trans ; 48(2): 395-399, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30523349

RESUMO

Three tetracoordinated cobalt(ii) complexes with a series of unsymmetrical bidentate ligands were synthesized and crystallographically characterized. Although their static magnetic properties are similar, their dynamic magnetic properties differ drastically depending indirectly on intermolecular hydrogen-bonding interactions.

3.
Chem Commun (Camb) ; 54(64): 8869-8872, 2018 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-30042991

RESUMO

A new cobalt(ii) complex bearing a pair of cobalt(iii) tris-chelate complexes as metalloligands was prepared. The CoII ion possesses an ideal trigonal antiprismatic geometry because of the intermolecular hydrogen-bonds between the metalloligands via counter anions. This complex exhibits slow magnetic relaxation under a dc field reminiscent of a single-molecule magnet behavior.

4.
Dalton Trans ; 46(46): 16306-16314, 2017 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-29140393

RESUMO

The magnetostructural correlation of the hexakis-dmso cobalt(ii) complex, [Co(dmso)6](BPh4)2 (dmso: dimethylsulfoxide), was investigated by single-crystal X-ray diffraction study and magnetic measurements. The magnetic analysis concluded the negative Δ value (H = Δ(L - 2/3) + E(L - L) - (3/2)κλL·S + ß[-(3/2)κLu + geSu]·Hu (u = x, y, z)), and this was explained by the tetragonal elongation of the octahedral geometry. The magnetostructural correlation was ascertained by both the angular overlap model calculation and the density functional theory calculation.

5.
Inorg Chem ; 56(1): 138-146, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27976888

RESUMO

Magnetic properties of dinuclear nickel(II) complex [Ni2(sym-hmp)2](BPh4)2·3.5DMF·0.5(2-PrOH) (1), where (sym-hmp)- is 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate anion and DMF indicates dimethylformamide, were investigated using high-frequency and -field electron paramagnetic resonance (HFEPR). To magnetically characterize the mononuclear nickel(II) species forming the dimer, its two dinuclear zinc(II) analogues, [Zn2(sym-hmp)2](BPh4)2·3.5DMF·0.5(2-PrOH) (2) and [Zn2(sym-hmp)2](BPh4)2·2acetone·2H2O (2'), were prepared. One of them (2') was structurally characterized by X-ray diffractometry and doped with 5% mol nickel(II) ions to prepare a mixed crystal 3. From the HFEPR results on complex 1 obtained at 40 K, the spin Hamiltonian parameters of the first excited spin state (S = 1) of the dimer were accurately determined as |D1| = 9.99(2) cm-1, |E1| = 1.62(1) cm-1, and g1 = [2.25(1), 2.19(2), 2.27(2)], and for the second excited spin state (S = 2) at 150 K estimated as |D2| ≈ 3.5 cm-1. From these numbers, the single-ion zero-field splitting (ZFS) parameter of the Ni(II) ions forming the dimer was estimated as |DNi| ≈ 10-10.5 cm-1. The HFEPR spectra of 3 yielded directly the single-ion parameters for DNi = +10.1 cm-1, |ENi| = 3.1 cm-1, and giso = 2.2. On the basis of the HFEPR results, the previously obtained magnetic data (Sakiyama, H.; Tone, K.; Yamasaki, M.; Mikuriya, M. Inorg. Chim. Acta 2011, 365, 183) were reanalyzed, and the isotropic interaction parameter between the Ni(II) ions was determined as J = -70 cm-1 (Hex = -J SA·SB). Finally, density functional theory calculations yielded the J value of -90 cm-1 in a qualitative agreement with the experiment.

6.
Chemistry ; 22(2): 724-35, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26728231

RESUMO

Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high-spin cobalt(II) complexes, namely [Co(II) (dmf)6 ](BPh4 )2 (1) and [Co(II) 2 (sym-hmp)2 ](BPh4 )2 (2), in which dmf=N,N-dimethylformamide; sym-hmp=2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate, and BPh4 (-) =tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual Co(II) site. In compound 1, this approach reveals the correlation between the single-ion easy magnetization direction and a trigonal elongation axis of the Co(II) coordination octahedron. In exchange-coupled dimer 2, the determination of the individual Co(II) magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both Co(II) sites deviate from the single-ion behavior because of antiferromagnetic exchange coupling.

7.
Dalton Trans ; 44(30): 13439-43, 2015 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-26150171

RESUMO

A large up-field shift (-763 ppm) has been observed for the carboxyl carbons of the dichlorido complex TBA[Ru(2)(O(2)CCH(3))(4)Cl(2)] (TBA(+) = tetra(n-butyl)ammonium cation) in the (13)C NMR spectrum (CD(2)Cl(2) at 25 °C). The DFT calculations showed spin delocalization from the paramagnetic Ru(2)(5+) core to the ligands, in agreement with the large up-field shift.

8.
Chemistry ; 20(31): 9693-701, 2014 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-24981819

RESUMO

A series of bis-chelate pseudo-octahedral mononuclear coordination complexes of manganese with the chromophore [MnN4 O2 ](n+) (n=0, 1) have been generated in all three principal oxidation states of this transition-metal center under ambient conditions by utilizing a readily tunable, versatile phenolic pyridylhydrazone ligand system (i.e., H2 (3,5-R(1) ,R(2) )-L; L=ligand). Strategic combinations of the nature and position of a variety of substituent groups afforded selective, spontaneous stabilization of multiple spin states of the manganese center, which, upon close crystallographic scrutiny, appears to be in part due to the occurrence or absence of hydrogen-bonding interactions that involve the phenolate/phenolic oxygen atom. The divalent complexes are isolable in two forms, namely, molecular [Mn(II) {H(3,5-R(1) ,R(2) )-L}2 ] and ionic [Mn(II) {H2 (3,5-R(1) ,R(2) )-L}{H(3,5-R(1) ,R(2) )-L}]ClO4 , with the latter complex converting easily into the former complex on deprotonation. Accessibility of the higher-valent states is achievable only when the phenolate oxygen atom is sterically hindered from participation in hydrogen bonding. The [Mn(III) {H(3,5-tBu2 )-L}2 ]ClO4 complex is the first example of a hydrazone-based Mn(III) complex to exhibit spin crossover. Formation of the tetravalent complexes [Mn(IV) {(3,5-R(1) ,R(2) )-L}2 ] (R(1) =tBu, R(2) =H; R(1) =R(2) =tBu) necessitates base-assisted abstraction of the hydrazinic proton.

9.
Inorg Chem ; 51(22): 12503-10, 2012 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-23134429

RESUMO

Reactions of M(OAc)2·4H2O (M = Ni, Co) with 3-[benzyl(2-hydroxyethyl)amino]-1-propanol (H2L) in the presence of pyridine or triethylamine afforded novel homometallic icosanuclear wheel-shaped complexes [M20L4(HL)4(OAc)28] (M = Ni (1), Co (2)), which consist of a central M(II)12 single-stranded, nearly planar loop with four peripheral [M2(HL)(OAc)2] fragments attached in an S4 symmetrical fashion. The complexes can alternatively be recognized as saddle-shaped wheel structures, in which four tetranuclear units of [M4L(HL)(OAc)7](2-) are connected by four M(2+) ions (M5). The tetranuclear unit itself can be derived from an ideal C2 symmetrical [M4(HL)2(µ-η(2)-OAc)4(µ-η(1),η(1)-OAc)2(η(1),η(1)-OAc)](-) structure through deprotonation of the HL(-) ligand, and is composed of two plane-shared M3O4 incomplete cubanes in which the M2 and M3 atoms are involved in the central fused plane and the M1 and M4 atoms are disposed at the apex sites. Mixed-metal icosanuclear complexes [NixM20-xL4(HL)4(OAc)28] (3, M = Co, x = 9.5) and [Ni12M8L4(HL)4(OAc)28] (4, M = Cu) were also synthesized by using equimolar amounts of Ni(II) and M(II) ions, and were shown to have similar structures to 1 and 2. X-ray crystallographic and fluorescent analyses revealed that complex 3 contains nonstoichiometric amounts of Ni(2+) and Co(2+) ions in the ratio of 9.5:10.5 and that these are disordered at every metal site. In striking contrast, complex 4 has a stoichiometric formula of Ni12Cu8, which was confirmed by the Jahn-Teller elongation of Cu(2+) ions, and consequently, the M2 and M5 positions are occupied exclusively by the Cu(2+) ions. The temperature-dependent direct current (dc) magnetic susceptibility data showed the presence of ferromagnetic exchange interactions in the Ni homometallic (1) and NiCu bimetallic (4) complexes, while the Co homometallic (2) and NiCo bimetallic (3) complexes exhibited antiferromagnetic interactions due to spin-orbit coupling effects of the octahedral Co(II) ions. The present results demonstrate that the unsymmetrical aminoalcohol ligand H2L is quite effective in organizing the homo- and heterometallic icosanuclear wheel-shaped metal arrangements.

10.
Dalton Trans ; 41(8): 2500-14, 2012 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-22216420

RESUMO

The two potentially tridentate and monoprotic Schiff bases acetylpyridine benzoylhydrazone (HL(1)) and acetylpyridine 4-tert-butylbenzoylhydrazone (HL(2)) demonstrate remarkable coordination versatility towards iron on account of their propensity to undergo tautomeric transformations as imposed by the metal centre. Each of the pyridyl aroylhydrazone ligands complexes with the ferrous or ferric ion under strictly controlled reaction conditions to afford three six-coordinate mononuclear compounds [Fe(II)(HL)(2)](ClO(4))(2), [Fe(II)L(2)] and [Fe(III)L(2)]ClO(4) (HL = HL(1) or HL(2)) displaying distinct colours congruent with their intense CT visible absorptions. The synthetic manoeuvres rely crucially on the stoichiometry of the reactants, the basicities of the reaction mixtures and the choice of solvent. Electrochemically, each of these iron compounds exhibits a reversible metal-centred redox process. By all appearances, [Fe(III)(L(1))(2)]ClO(4) is one of only two examples of a crystallographically elucidated iron(III) bis-chelate compound of a pyridyl aroylhydrazone. Several pertinent physical measurements have established that each of the Schiff bases stabilises multiple spin states of iron; the enolate form of these ligands exhibits greater field strength than does the corresponding neutral keto tautomer. To the best of our knowledge, [Fe(III)(L(1))(2)]ClO(4) and [Fe(III)(L(2))(2)]ClO(4) are the first examples of ferric spin crossovers of aroylhydrazones. Whereas in the former the spin crossover (SCO) is an intricate gradual process, in the latter the (6)A(1)↔(2)T(2) transition curve is sigmoidal with T(½)∼280 K and the SCO is virtually complete. As regards [Fe(III)(L(1))(2)]ClO(4), Mössbauer and EPR spectroscopic techniques have revealed remarkable dependence of the spin transition on sample type and extent of solvation. In frozen MeOH solution at liquid nitrogen temperature, both iron(III) compounds exist wholly in the doublet ground state.


Assuntos
Hidrazonas/química , Ferro/química , Compostos Organometálicos/química , Piridinas/química , Cristalografia por Raios X , Eletroquímica , Ligantes , Fenômenos Magnéticos , Compostos Organometálicos/síntese química
11.
Chem Commun (Camb) ; (13): 1664-6, 2009 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-19294255

RESUMO

Elastic pentacopper molecular chains, [Cu5(panapy)4X2] (X=Cl (), Br ()) and [Cu5(panapy)4]X'2 (X'=BF4 (), PF6 ()), were prepared using a naphthyridine-modulated N6-donor ligand, panapy2-, and showed magnetically coupled, dynamic rearrangement of five Cu(II) ions switched by the presence/absence of halide termination.

12.
Inorg Chem ; 46(23): 9531-3, 2007 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-17941632

RESUMO

Photoinduced dissociation of two Mo-CN bonds in [Mo(CN)8]4- affords the octahedral complex anion [Mo(CN)6]2-. This hexacyanomolybdate(IV) ion is also obtainable from tetracyanooxomolybdate via a thermal substitutional synthetic route. The anion represents the missing link in the ligand-field photolysis of octacyanomolybdate(IV); it is characterized by means of single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility measurements as well as IR, Raman, 1H and 13C NMR, and electronic spectroscopy.

13.
Inorg Chem ; 46(23): 9558-68, 2007 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-17918825

RESUMO

The six-coordinate mononuclear iron(III) complexes [Fe(salpm)2]ClO(4).0.5EtOH, [Fe(salpm)2]Cl, [Fe{(3,5-tBu2)-salpm}2]X (X=ClO4- or Cl-), and [Fe{(3,5-tBu2)-salpm}2]NO(3).2H2O [Hsalpm=N-(pyridin-2-ylmethyl)salicylideneamine; H(3,5-tBu2)-salpm=N-(pyridin-2-ylmethyl)-3,5-di-tert-butylsalicylideneamine] have been synthesized and isolated in crystalline form; their chemical identities have been ascertained by elemental analyses, FAB mass spectrometry, and infrared spectroscopy. The room-temperature effective magnetic moments [(8chiMT)1/2 approximately 5.85-5.90 microB] of these complexes are consistent with the high-spin (S=5/2) ground state. These complexes are intensely colored on account of the strong ppi-->dpi* LMCT visible absorptions. Definitive evidence for the structures of [Fe(salpm)2]ClO(4).0.5EtOH and [Fe{(3,5-tBu2)-salpm}2]NO(3).2H2O has been provided by single-crystal X-ray crystallography. The monomeric complex cations in both compounds comprise two uninegative phenolate-pyridyl tridentate Schiff-base ligands coordinated meridionally to the iron(III) to afford a distorted octahedral geometry with a trans,cis,cis-[FeO2N4] core. Whereas [Fe(salpm)2]ClO(4).0.5EtOH undergoes a thermally induced 6A1<-->2T2 crossover, [Fe{(3,5-tBu2)-salpm}2]NO(3).2H2O retains its spin state in the solid state down to 5 K. However, EPR spectroscopy reveals that the latter complex does exhibit a spin transformation in solution, albeit to a much lesser extent than does the former. The spin crossover in [Fe(salpm)2]ClO(4).0.5EtOH has resulted in an unprecedented crystallographic observation of the coexistence of high-spin and low-spin iron(III) complex cations in equal proportions around 100 K. At room temperature, the two crystallographically distinct ferric centers are both high spin; however, one [Fe(salpm)2]+ complex cation undergoes a complete spin transition over the temperature range approximately 200-100 K, whereas the other converts very nearly completely between 100 and 65 K; approximately 10% of the complex cations in [Fe(salpm)2]ClO(4).0.5EtOH remain in the high-spin state down to 5 K.

14.
Dalton Trans ; (30): 3330-4, 2007 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-17893780

RESUMO

Quinoline-based, tetradentate nitrogen ligands, N,N'-bis(2-quinolylmethyl)-N,N'-dialkyl-1,2-ethanediamine (alkyl = methyl, bqdmen; ethyl, bqdeen; isopropyl, bqdpen), have been investigated as the supporting ligands for the formation of bis(micro-oxo) dinuclear manganese complexes. Bis(micro-oxo)Mn(2)(iii,iii) complexes and were obtained for bqdmen and bqdeen, respectively, as evidenced by X-ray crystallography, whereas bqdpen did not afford any manganese complexes due to its steric bulk. Complexes and exhibit highly positive Mn(2)(iii,iii)/Mn(2)(iii,iv) and Mn(2)(iii,iv)/Mn(2)(iv,iv) redox couples relative to the corresponding pyridine-ligated (micro-O)(2)Mn(2)(iii,iii) complexes.


Assuntos
Manganês/química , Nitrogênio/química , Compostos Organometálicos/química , Quinolinas/química , Cristalografia por Raios X , Eletroquímica , Ligantes , Estrutura Molecular , Compostos Organometálicos/síntese química , Oxirredução
15.
Inorg Chem ; 45(17): 6646-60, 2006 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-16903719

RESUMO

Tetranuclear copper(II) complexes containing alpha-D-glucose-1-phosphate (alpha-D-Glc-1P), [Cu4(mu-OH){mu-(alpha-D-Glc-1P)}2(bpy)4(H2O)2]X3 [X = NO3 (1a), Cl (1b), Br (1c)], and [Cu4(mu-OH){mu-(alpha-D-Glc-1P)}2(phen)4(H2O)2](NO3)3 (2) were prepared by reacting the copper(II) salt with Na2[alpha-D-Glc-1P] in the presence of diimine ancillary ligands, and the structure of 2 was characterized by X-ray crystallography to comprise four {Cu(phen)}2+ fragments connected by the two sugar phosphate dianions in 1,3-O,O' and 1,1-O mu4-bridging fashion as well as a mu-hydroxo anion. The crystal structure of 2 involves two chemically independent complex cations in which the C2 enantiomeric structure for the trapezoidal tetracopper(II) framework is switched according to the orientation of the alpha-D-glucopyranosyl moieties. Temperature-dependent magnetic susceptibility data of 1a indicated that antiferromagnetic spin coupling is operative between the two metal ions joined by the hydroxo bridge (J = -52 cm(-1)) while antiferromagnetic interaction through the Cu-O-Cu sugar phosphate bridges is weak (J = -13 cm(-1)). Complex 1a readily reacted with carboxylic acids to afford the tetranuclear copper(II) complexes, [Cu4{mu-(alpha-D-Glc-1P)}2(mu-CA)2(bpy)4](NO3)2 [CA = CH3COO (3), o-C6H4(COO)(COOH) (4)]. Reactions with m-phenylenediacetic acid [m-C6H4(CH2COOH)2] also gave the discrete tetracopper(II) cationic complex [Cu4{mu-(alpha-D-Glc-1P)}2(mu-m-C6H4(CH2COO)(CH2COOH))2(bpy)4](NO3)2 (5a) as well as the cluster polymer formulated as {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-m-C6H4(CH2COO)2)(bpy)4](NO3)2}n (5b). The tetracopper structure of 1a is converted into a symmetrical rectangular core in complexes 3, 4, and 5b, where the hydroxo bridge is dissociated and, instead, two carboxylate anions bridge another pair of Cu(II) ions in a 1,1-O monodentate fashion. The similar reactions were applied to incorporate sugar acids onto the tetranuclear copper(II) centers. Reactions of 1a with delta-D-gluconolactone, D-glucuronic acid, or D-glucaric acid in dimethylformamide resulted in the formation of discrete tetracopper complexes with sugar acids, [Cu4{mu-(alpha-D-Glc-1P)}2(mu-SA)2(bpy)4](NO3)2 [SA = D-gluconate (6), D-glucuronate (7), D-glucarateH (8a)]. The structures of 6 and 7 were determined by X-ray crystallography to be almost identical with that of 3 with additional chelating coordination of the C-2 hydroxyl group of D-gluconate moieties (6) or the C-5 cyclic O atom of D-glucuronate units (7). Those with D-glucaric acid and D-lactobionic acid afforded chiral one-dimensional polymers, {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-D-glucarate)(bpy)4](NO3)2}n (8b) and {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-D-lactobionate)(bpy)4(H2O)2](NO3)3}n (9), respectively, in which the D-Glc-1P-bridged tetracopper(II) units are connected by sugar acid moieties through the C-1 and C-6 carboxylate O atoms in 8b and the C-1 carboxylate and C-6 alkoxy O atoms of the gluconate chain in 9. When complex 7 containing d-glucuronate moieties was heated in water, the mononuclear copper(II) complex with 2-dihydroxy malonate, [Cu(mu-O2CC(OH)2CO2)(bpy)] (10), and the dicopper(II) complex with oxalate, [Cu2(mu-C2O4)(bpy)2(H2O)2](NO3)2 (11), were obtained as a result of oxidative degradation of the carbohydrates through C-C bond cleavage reactions.


Assuntos
Cobre/química , Glucofosfatos/química , Açúcares Ácidos/química , Ácidos Carboxílicos/química , Dicroísmo Circular , Dissacarídeos/química , Ácido Glucárico/química , Ligação de Hidrogênio , Ligantes , Modelos Moleculares , Estrutura Molecular , Oxirredução , Polímeros/química , Espectrometria de Massas por Ionização por Electrospray , Estereoisomerismo
16.
Inorg Chem ; 45(18): 7100-4, 2006 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-16933909

RESUMO

The photoinduced dissociation of a W-CN bond in [W(CN)8]4- in an aqueous solution under ambient conditions, in conjunction with the uptake of molecular oxygen, affords the W(VI) mixed-ligand complex anion [W(CN)(7)(eta2-O2)]3-, conveniently isolable as its [PPh4+] salt. Although research into the chemistry of cyanomolybdates and cyanotungstates has been pursued with great interest and vigor over several decades, there is a paucity of structurally characterized cyano-peroxo complexes of Mo and W. The side-on coordination mode of the peroxo moiety in [W(CN)7(eta2-O2)]3- has been ascertained with X-ray crystal structure determination [d(O-O) = 1.41 A; peroxo bite angle: 41.0 degrees ] and corroborated with vibrational spectroscopy [nu(O-O) = 915 cm(-1)]. The complex ion exhibits trapezoidal tridecahedral geometry and represents the new class of nine-coordinate complexes with one bidentate and seven monodentate ligands. Cyclic voltammetry shows a reversible redox behavior of [W(CN)7(eta2-O2)]3- in CH3CN with its standard reduction potential equal to 1.130 V. Generally, interest in atmospheric oxygen derives from the versatility of this molecule as a ligand and oxidant and extends to the physicochemical features it imparts to transition metals such as copper and iron in biological oxygen carriers.


Assuntos
Compostos Organometálicos/química , Tungstênio/química , Cristalografia por Raios X , Ligantes , Modelos Moleculares , Compostos Organometálicos/síntese química
17.
Inorg Chem ; 45(7): 2925-41, 2006 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-16562948

RESUMO

Reactions of CuX2.nH2O with the biscarboxylate ligand XDK (H2XDK = m-xylenediamine bis(Kemp's triacid imide)) in the presence of N-donor auxiliary ligands yielded a series of dicopper(II) complexes, [Cu2(mu-OH)(XDK)(L)2]X (L = N,N,N',N'-tetramethylethylenediamine (tetmen), X = NO3 (1a), Cl (1b); L = N,N,N'-trimethylethylenediamine (tmen), X = NO3 (2a), Cl (2b); L =2,2'-bipyridine (bpy), X = NO3 (3); L = 1,10-phenanthroline (phen), X = NO3 (4); L = 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), X = NO3 (5); L = 4-methyl-1,10-phenanthroline (Mephen), X = NO3 (6)). Complexes 1-6 were characterized by X-ray crystallography (Cu...Cu = 3.1624(6)-3.2910(4) A), and the electrochemical and magnetic properties were also examined. Complexes 3 and 4 readily reacted with diphenyl phosphoric acid (HDPP) or bis(4-nitrophenyl) phosphoric acid (HBNPP) to give [Cu2(mu-phosphate)(XDK)(L)2]NO3 (L = bpy, phosphate = DPP (11); L = phen, phosphate = DPP (12), BNPP (13)), where the phsophate diester bridges the two copper ions in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.268(3)-4.315(1) A). Complexes 4 and 6 with phen and Mephen have proven to be good precursors to accommodate a series of sugar monophosphate esters (Sugar-P) onto the biscarboxylate-bridged dicopper centers, yielding [Cu2(mu-Sugar-P)(XDK)(L)2] (Sugar-P = alpha-D-Glc-1-P (23a and b), D-Glc-6-P (24a and b), D-Man-6-P (25a), D-Fru-6-P (26a and b); L = phen (a), Mephen (b)) and [Cu2(mu-Gly-n-P)(XDK)(Mephen)2] (Gly-n-P = glycerol n-phosphate; n = 2 (21), 3 (22)), where Glc, Man, and Fru are glucose, mannose, and fructose, respectively. The structure of [Cu2(mu-MNPP)(XDK)(phen)2(CH3OH)] (20) was characterized as a reference compound (H2MNPP = 4-nitrophenyl phosphoric acid). Complexes 4 and 6 also reacted with d-fructose 1,6-bisphosphate (D-Fru-1,6-P2) to afford the tetranuclear copper(II) complexes formulated as [Cu4(mu-D-Fru-1,6-P2)(XDK)2(L)4] (L = phen (27a), Mephen (27b)). The detailed structure of 27a was determined by X-ray crystallography to involve two different tetranuclear complexes with alpha- and beta-anomers of D-Fru-1,6-P2, [Cu4(mu-alpha-D-Fru-1,6-P2)(XDK)2(phen)4] and [Cu4(mu-beta-D-Fru-1,6-P2)(XDK)2(phen)4], in which the D-Fru-1,6-P2 tetravalent anion bridges the two [Cu2(XDK)(phen)2]2+ units through the C1 and C6 phosphate groups in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.042(2)-4.100(2) A). Notably, the structure with alpha-D-Fru-1,6-P2 demonstrated the presence of a strong hydrogen bond between the C2 hydroxyl group and the C1 phosphate oxygen atom, which may support the previously proposed catalytic mechanism in the active site of fructose-1,6-bisphosphatase.


Assuntos
Cobre/química , Frutose-Bifosfatase/química , Modelos Químicos , Compostos Organometálicos/química , Organofosfatos/química , Sítios de Ligação , Cristalografia por Raios X , Eletroquímica , Ligação de Hidrogênio , Ligantes , Magnetismo , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química , Estereoisomerismo
18.
Inorg Chem ; 45(7): 3048-56, 2006 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-16562961

RESUMO

Two new dinuclear Ru(III) complexes containing naphthalene moieties, K[Ru2(dhpta)(mu-O2CCH2-1-naph)2] (1) and K[Ru2(dhpta)(mu-O2CCH2-2-naph)2] (2) (H5dhpta = 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, naph-1-CH2CO2H = 1-naphthylacetic acid, naph-2-CH2CO2H = 2-naphthylacetic acid), were synthesized. Complex 2 crystallized as an orthorhombic system having a space group of Pbca with unit cell parameters a = 10.6200(5) A, b = 20.270(1) A, c = 35.530(2) A, and Z = 8. EXAFS analysis of 1 and 2 in the solid states and in solution clarified that the dinuclear structures of 1 and 2 were kept in DMSO solutions. Variable-temperature magnetic susceptibility data indicated that the two Ru(III) centers are strongly antiferromagnetically coupled as shown by the large coupling constants, J = -581 cm(-1) (1) and -378 cm(-1) (2). In the cyclic voltammograms of 1 and 2, one oxidation peak and two reduction peaks which were assigned to the redox reaction of the ruthenium moieties were observed in DMF. The large conproportionation constants estimated from the reduction potentials of Ru(III)Ru(III) and Ru(III)Ru(II) indicated the great stability of the mixed-valent state. The mixed-valent species [Ru(III)Ru(II)(dhpta)(mu-O2CCH2-R)2](2-) (R = 1-naph (6) and R = 2-naph (7)) were prepared by controlled potential electrolysis of 1 and 2 in DMF. The electronic absorption spectra of 6 and 7 were similar to that of [Ru(III)Ru(II) (dhpta)(mu-O2CCH3)2](2-) which is a typical Class II type mixed-valent complex. The fluorescence decay of 1 and 2 indicated that there are two quenching processes which come from the excimer and monomer states. The short excimer lifetimes of 1 and 2 were ascribed to the energy transfer from the naphthyl moieties to the Ru centers. The different excimer ratio between 1 and 2 suggested that the excimer formation is affected by the conformation of the naphthyl moieties in the diruthenium(III) complexes.


Assuntos
Ácidos Naftalenoacéticos/química , Compostos Organometálicos/química , Rutênio/química , Eletroquímica , Ligantes , Espectroscopia de Ressonância Magnética , Magnetismo , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química , Fotoquímica , Sensibilidade e Especificidade , Estereoisomerismo , Temperatura
19.
Inorg Chem ; 45(5): 2083-92, 2006 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-16499370

RESUMO

A new sugar-derived Schiff's base ligand N-(3-tert-butyl-2-hydroxybenzylidene)-4,6-O-ethylidene-beta-D-glucopyranosylamine (H3L1) has been developed which afforded the coordinatively labile, alcoholophilic trinuclear Cu(II) complex [Cu3(L1)2(CH3OH)(H2O)] (1). Complex 1 has been further used in the synthesis of a series of alcohol-bound complexes with a common formula of [Cu3(L1)2(ROH)2] (R = Me (2), Et (3), nPr (4), nBu (5), nOct (6)). X-ray structural analyses of complexes 2-6 revealed the collinearity of trinuclear copper(II) centers with Cu-Cu-Cu angles in the range of 166-172 degrees . The terminal and central coppers are bound with NO3 and O4 atoms, respectively, and exhibit square-planar geometry. The trinuclear structures of 2-6 can be viewed as the two {Cu(L1)}- fragments capture a copper(II) ion in the central position, which is further stabilized by a hydrogen-bonding interaction between the alcohol ligands and the sugar C-3 alkoxo group. Complex 2 exhibits a strong antiferromagnetic interaction between the Cu(II) ions (J = -238 cm(-1)). Diffusion of methanol into a solution of complex 1 in a chloroform/THF mixed solvent afforded the linear trinuclear complex [Cu(3)(L1)2(CH3OH)2(THF)2] (7). The basic structure of 7 is identical to complex 2; however, THF binding about the terminal coppers (Cu-O(THF) = 2.394(7) and 2.466(7) A) has introduced the square-pyramidal geometry, indicating that the planar trinuclear complexes 2-6 are coordinatively unsaturated and the terminal metal sites are responsible for further ligations. In the venture of proton-transfer reactions, a successful proton transfer onto the saccharide C-3 alkoxo group has been achieved using 4,6-O-ethylidene-d-glucopyranose, resulting in the self-assembled tetranuclear complex, [Cu4(HL1)4] (8), consisting of the mononuclear Cu(II) chiral building blocks, {Cu(HL1)}.


Assuntos
Carboidratos/química , Cobre/química , Química Inorgânica/métodos , Cristalografia por Raios X , Ligantes , Estrutura Molecular , Prótons , Bases de Schiff
20.
Inorg Chem ; 44(21): 7268-70, 2005 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-16212339

RESUMO

A new heptadentate N6-O1 ligand, N,N,N',N'-tetrakis(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine (Htqhpn), was synthesized and used to generate compounds with linearly ordered MnIIMnIIIMnIIIMnII tetranuclear cores. This is the lowest valent tetranuclear manganese complex that exhibits a (mu2-O)2Mn2 core in the molecule. The electron paramagnetic resonance and magnetic measurements of these tetranuclear complexes suggest moderately strong antiferromagnetic coupling for the central MnIII2 core, with weak coupling between the MnII and MnIII centers.

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